An ethylene-α-olefin-non-conjugated diene copolymer has hitherto been produced with a homogeneous vanadium catalyst (for example, JP 46-21212B).
There is also known a process for producing a branched chain-containing ethylene-α-olefin copolymer using a combination of the above-mentioned vanadium catalyst with a component functioning as a Lewis base (for example, JP47-23413B).
There is further known a polymerization process, wherein an organic aluminum compound, a vanadium compound, a halogenated hydrocarbon and a component functioning as a Lewis base are supplied to a polymerization reactor without preliminary contact of (1) the organic aluminum compound and the vanadium compound, (2) the organic aluminum compound and the halogenated hydrocarbon, or (3) the organic aluminum compound, the vanadium compound and the halogenated hydrocarbon (for example, JP 07-048412A).